Safety device for gas-fired furnaces and the like



Nov. 3, 1970 J. N. IGNAZIQ 3,537,803

SAFETY DEVICE FOR GAS-FIRED FURNACES AND THE LIKE Original Filed Feb. 19, 1968 INVENTOR. JOSEPH N. IGNAZIO AGENT United States Patent 3,537,803 SAFETY DEVICE FOR GAS-FIRED FURNACES AND THE LIKE Joseph N. Ignazio, 1655 Lancaster Drive, Youngstown, Ohio 44511 Continuation of application Ser. No. 706,355, Feb. 19, 1968. This application Oct. 29, 1969, Ser. No. 872,420 Int. Cl. F23h /24 US. Cl. 431-22 2 Claims ABSTRACT OF THE DISCLOSURE A temperature sensing unit is mounted above the primary, secondary air inlet and/or the draft-diverter inlet of a gas-fired furnace. The sensing device is operative to shut off the fuel supply to the furnace in the event the temperature rises above normal, which occurs when there is any obstruction of the flue or chimney serving the furnace. A mounting box for improved sensitivity is also provided.

This is a continuation of application Ser. No. 706,355, filed Feb. 19, 1968 and now abandoned.

This invention relates to gas-fired furnaces and the like and more particularly to a safety device which automatically shuts off the fuel supply to the furnace in the event there is an obstruction of the combustion chamber, flue, or chimney or if the firing rate of the furnace is excessive.

If for any reason the normal escape path for the combustion products of a gas furnace becomes obstructed the exhaust gases escaped either through the draft diverter opening of the flue or the primary secondary air opening of the combustion chamber. Such a condition may continue unnoticed for a substantial period of time with detrimental and sometimes fatal results. Gas furnaces such as are installed in home heating systems are normally provided with adequate safety devices to protect against over heating of the flue and combustion chamber and to prevent the escape of gas in the event the pilot light is blown out, but these furnaces are normally not provided with any means for shutting down the furnace if the flue or chimney becomes obstructed. While gas analyzers may be used to sense the presence of carbon monoxide, such devices are not practical for home use and consequently are not normally used in conjunction with heating furnaces.

It is the primary object of the present invention to provide a device which shuts off the fuel supply of the furnace in the event there is any obstruction in the normal escape path of the exhaust gases. It is a further object of my invention to provide such a device which is of a high degree of reliability and which is capable of being manufactured and installed at a low cost. Another object of my invention is provision of such a device which may be readily adapted to existing or new equipment with a minimum of modification thereto.

The above and other objects and advantages of my invention will become apparant upon consideration of the following specification and the accompanying drawing wherein there is shown a preferred embodiment of my invention.

In the drawing:

FIG. 1 is a front elevational view of a typical gas furnace showing schematically the installation of my safety device thereto;

FIG. 2 is a side elevational view, in section, of the furnace of FIG. 1 showing the flow of air and exhaust .gases under normal operating conditions;

FIG. 3 is a view similar to FIG. 2 but showing the flow of air and exhaust gases when the chimney serving the furnace is blocked by an obstruction;

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FIG. 4 is an isometric view of the mounting box for the temperature sensing device of my invention; and

FIG. 5 is a sectional view taken along the line VV of FIG. 4.

Reference numeral 10 designates generally a gas-fired furnace of the counter-flow type. It will be understood that this type of furnace is chosen for illustrative reasons only and that the invention may be applied to any type of gasfired furnace. The furnace 10 is connected to a gas line 11 and is provided with the normal controls 12 which are responsive to the thermostat and to the stack temperature safety switches, as is common practice. The furnace is also provided with a burner 13, combustion chamber 14, flue 15 which connects with a chimney 16, with a primary secondary air opening 17 and with a draft diverter opening 18, all the accordance with common practice. Under normal operating conditions air (indicated by solid arrows in the drawing), enters the opening 17 and combines with the gas in the combustion chamber where it is burned. The exhaust gases (indicated by broken arrows) are carried upward through the chamber 14, the flue 15 to the chimney 16 and are there exhausted from the building. Some fresh air also enters the draft diverter opening 18 and is carried upward along with the gases from the combustion chamber. If, for any reason, the chimney becomes obstructed as shown at 19 in FIG. 3 the exhaust gases are no longer exhausted through the chimney but rather escape by the openings 17 and 18, introducing deadly carbon monoxide into the dwelling.

In order to rapidly sense any such malfunction of the furnace I provide temperature sensing devices indicated generally by reference numeral 20, immediately above the primary air opening 17 and the draft diverter opening 18 of the furnace. Under normal operating conditions such as those shown in FIG. 2 cool air is drawn by these devices and they remain inoperative. However, if there is an obstruction of the chimney, as shown in FIG. 3, or of the flue 15 or the upper portion of the combustion chamber 14, the exhaust gases and heated air escape through the openings 17 and 18 over the sensing device 20 triggering the temperature sensing units which are connected to a solenoid operated valve 21. The triggering of any of the sensing devices 20 immediately activates the solenoid valve 21 shutting off the fuel supply to the furnace.

I have found a preferred embodiment of the sensing device 20 consists of a manually resettable thermal disk 22 mounted on the upper end of a hood-like box 23. The thermal disk 22 is of standard construction and has a reset button 24 which provides a visible indication when overheating has occurred. The disk 22 is also provided with a pair of terminals 25 for connecting the disk to the solenoid control circuit. The box 23 directs a portion of the escaping exhaust gases toward the sensing disk 22, holes 26 being provided to insure a flow of gas through the box 23. The box 23 also protects the sensing disk 22 from drafts which tend to effect the reliability of the sensor. In the embodiment shown the sensor mounting box 23 is provided with a pair of lugs 23' for attaching the unit to the furnace but it will be understood that any suitable mounting means may be used.

The control circuit for the sensing elements 20 and the solenoid valve 21 is not illustrated in detail as the particular circuit employed will be determined by the characteristics of the solenoid 21 and the sensing disk 22, i.e., whether the solenoid opens or closes the gas line when energized and whether the sensing disk opens or closes the circuit when the temperature of the gases passing through the funnelling box 23 raises above a predetermined level. The details of the control circuit will be readily apparent to one skilled in the art when the characteristics of the control elements are known.

It will be understood that while two sensing elements are shown in the embodiment illustrated, more elements may be used on larger furnaces as desired. Also, the use of this safety system is not limited strictly to furnaces but may be used on other gas appliances as Well.

As the above and other changes may be made in and to my invention reference should be had to the appended claims in determining the true scope of the invention.

I claim:

1. In a gas-fired furnace having an enclosure, a combustion chamber within said enclosure, a flue connected to said combustion chamber for conducting the exhaust gases from said combustion chamber, a first opening in said enclosure admitting air into said combustion chamber, and a second opening in said enclosure serving as a draft diverter for said flue, the improvement comprising: a plurality of temperature sensing devices mounted externally of said combustion chamber, one of said temperature sensing devices being mounted on said enclosure immediately above said opening serving as a draft di- 4 verter; and means responsive to each of said temperature sensing devices for interrupting the fuel supply of said furnace when the temperature at any one of said sensing devices rises above a predetermined level.

2. The improvement according to claim 1 further including a second temperature sensing device mounted on said enclosure immediately above said first opening, said responsive means being operative upon the rising of the temperature at either of said sensing devices above said predetermined level.

References Cited UNITED STATES PATENTS EDWARD G. FAVORS, Primary Examiner U.S. Cl. X.R. 43177 

